1. Field of the Invention
The present invention relates to the fabrication of microscopic electromechanical devices. More specifically, the present invention relates to the fabrication of a phased micromirror array to facilitate programmable shaping of ultra-short optical pulses.
2. Related Art
xe2x80x9cFemtosecond pulse shapingxe2x80x9d has been developed to generate complicated, ultrafast optical pulses according to user specifications. The key component required to shape a femtosecond pulse is a versatile, high resolution, programmable spatial light phase modulator (SLPM). Recent attention has been focused on developing computer controlled programmable one-dimensional SLPMs for this pulse shaping. Existing linear SLPMs fall into two categories: deformable continuous thin membrane mirrors and pixilated arrays of liquid crystal phase shifters.
Deformation of a continuous membrane produces smooth spectral phase variations and a corresponding high quality optical pulse. Membranes, however, are not capable of producing localized abrupt spectral phase changes. On the other hand, a pixilated array of phase modulators can produce rapid phase changes between pixels. The phase shift for each pixel is constant, however, and the resulting stepwise approximation to smooth phase variations results in undesired energy in the pulse wings.
What is needed is an SLPM that facilitates programmable shaping of ultra-short optical pulses, which does not exhibit the drawbacks described above.
One embodiment of the present invention provides a spatial light phase modulator, which can perform piecewise linear phase modulation of a light beam. This spatial light phase modulator includes an array of movable micromirrors and an array of actuators. Each actuator of the array of actuators is movably coupled to one micromirror of the array of movable micromirrors and can move the micromirror both vertically and rotationally. These actuators are dual-mode actuators that can expand or contract to cause vertical motion and can tilt to cause rotational motion.
In one embodiment of the present invention, control signals applied to the array of actuators can cause the linear array of movable micromirrors to act in concert to perform piecewise linear phase modulation of the light beam.
In one embodiment of the present invention, vertical forces applied by the actuator can cause the micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.
In one embodiment of the present invention, the actuator includes a thermo-expansion actuator, a piezoelectric actuator, a magnoelectric actuator, or a capacitive actuator.
One embodiment of the present invention provides an optical function generator that is a femtosecond pulse shaper. This optical function generator includes a diffraction grating that disperses an input pulse into a dispersed spectrum, a lens assembly to focus the dispersed spectrum onto a micromirror array, and the micromirror array to provide spatial filtering to the dispersed spectrum to provide a filtered spectrum.
In one embodiment of the present invention, the lens assembly focuses the filtered spectrum on the diffraction grating. This diffraction grating then combines the filtered spectrum into an output pulse.
In one embodiment of the present invention, the optical function generator includes a plurality of actuators movably coupled to the micromirror array. Each actuator of the plurality of actuators can move one mirror of the micromirror array in both elevation and tilt.
One embodiment of the present invention provides a two-dimensional coherent mirror array that includes a two-dimensional micromirror array and a plurality of actuators movably coupled to this two-dimensional micromirror array. Each micromirror of the two-dimensional micromirror array is movably coupled to a triad of actuators positioned such that the micromirror can be elevated and tilted in any direction.
In one embodiment of the present invention, vertical forces applied by the triad of actuators can cause the micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.
In one embodiment of the present invention, an actuator of the plurality of actuators includes a thermo-expansion actuator, a piezoelectric actuator, a magnoelectric actuator, or a capacitive actuator.
One embodiment of the present invention provides a programmable micromirror array, including multiple movable micromirrors. A first movable comb is fixed to one edge of each of the movable micromirrors, and a second movable comb is fixed to the opposite edge of each movable micromirror. These movable combs form a movable portion of an interdigitated actuator coupled to each movable micromirror. This movable portion of the interdigitated actuator can apply vertical and rotational motions to the movable micromirrors.
In one embodiment of the present invention, the programmable micromirror array includes a first folded spring coupled to the distal end of the first movable comb, and a second folded spring coupled to the distal end of the second movable comb. These folded springs provide restoring forces to the movable portion of the interdigitated actuator.
In one embodiment of the present invention, the interdigitated actuator includes a fixed lower actuator and a fixed upper actuator. These fixed actuators act in concert to apply vertical and rotational forces to the movable portion of the interdigitated actuator.
In one embodiment of the present invention, the fixed lower actuator includes planar capacitive drives.
In one embodiment of the present invention, the fixed upper actuator includes vertical comb drives.
In one embodiment of the present invention, the vertical forces applied by the interdigitated actuator can cause the movable micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.
One embodiment of the present invention provides a two-dimensional programmable micromirror array including multiple hexagonally shaped, movable micromirrors. Each micromirror includes a first movable actuator fixed to a first edge of the micromirror, a second movable actuator fixed to a second edge of the micromirror, and a third movable actuator fixed to a third edge of the micromirror. These movable actuators are fixed to alternating edges of the micromirror, and act in concert to apply vertical and two-dimensional rotational motions to the micromirror. Note that each actuator applies vertical motions to one edge of the micromirror, and three actuators acting in concert apply rotational motions to the micromirror.
In one embodiment of the present invention, the movable micromirror includes a first folded spring coupled to the distal end of the first movable actuator, a second folded spring coupled to the distal end of the second movable actuator, and a third folded spring coupled to the distal end of the third movable actuator. These folded springs provides restoring forces to the movable micromirror.
In one embodiment of the present invention, the movable micromirror includes three actuators. Each actuator includes a movable actuator selected from the first movable actuator, the second movable actuator or the third movable actuator. Each actuator also includes a fixed lower actuator and a fixed upper actuator. These fixed lower and upper actuators can apply vertical and rotational forces to the movable micromirror through the movable actuator.
In one embodiment of the present invention, the fixed lower actuator includes planar capacitive drives.
In one embodiment of the present invention, the fixed upper actuator includes vertical comb drives.
In one embodiment of the present invention, vertical forces applied by the interdigitated actuator can cause the micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.